For transmission of service data between telecommunication devices, a service provider must set up and operate a network infrastructure. Operating mobile telephones with prepaid fees, i.e. in so-called prepaid mode, is known. With this type of operation, which, as a rule, does not require any subscription with a particular provider, the provider administers an accounting of charges which is identified by the calling line identification of the mobile telephone and, as a rule, through further identifiers, which are normally encrypted. The identifiers are stored at the provider and/or in the chip of the SIM card (Subscriber Identity Module), which must be present in the mobile telephone for the latter to be able to be operated for telecommunication. Such additional identifiers are certificates, for example, which confirm the authorization of the mobile telephone user, and are checked when establishing the connection. If the accounting of charges at the provider is supposed to be tracked in real time, then an updating must take place during a telephone call, for instance every second, based on the rate valid for the telephone call. This is in contrast to an accounting of charges in which calls are billed afterwards, and therefore the updating of the account of charges has to be carried out only at call end, for example. Mobile telephones in the prepaid mode can result in a very high technical investment for updating the account of charges.
Described in the German published patent application DE 100 39 434 A1 is a method for updating a counter of a terminal for accounting of charges. The counter is updated during a telephone call independently or according to control commands of the service provider at a certain clock pulse, and the authorization to use services is confirmed to the service provider at a certain clock pulse. In an embodiment, the counter is controlled or checked by the service provider by means of control commands. It is a drawback that the service provider needs a counter in order to check whether the certification for use of services was sent according to clock pulse. It is a further drawback that a corresponding counter image must be kept at the service provider in order to control the counter or to check the counter.
Known from the international patent application WO 03/079713 is a method of operation of mobile radio terminals in which WIM functionalities (Wireless Identification Module) are provided and billed, characterized in that the WIM is achieved internally, i.e. in the terminal or respectively in the SIM identification module located there. Each signature initiated by the participant is thereby counted internally, and, to be precise, back from a starting state, until the preset number of signatures is reached. The device is then blocked until a another signature count loading. Disadvantageous with this method is that, with the exception of blocking and release switches, the processing of the signature, i.e. of the digital data of the access rights, does not provide for any data processing and only performs a simple counting operation, without checking the volume of the digital data to be given a single signature, so that keeping service accounts at the provider is still necessary, it being necessary for a connection of the MSC (Mobile Switching Center) to the provider to be always established and maintained during a telephone call. During this step errors can occur, e.g. as a result of transmission interference or malfunction, so that the service accounts are able to be falsified. It is a further drawback that no volume-based billing is possible.